The present invention relates to a matrix type liquid crystal display panel which provides a visual display of intelligence signals such as digits, characters, symbols, patterns or the like through the use of a liquid crystal having an XY matrix type electrode structure consisting of a plurality of line electrodes and a plurality of column electrodes opposed thereto.
There are two basic types of electrode structure of a display panel utilizing a liquid crystal material or the like: the segment type and the XY matrix type. The former is useful to minimize the number of necessary display dots in displaying digits or the like of preselected shape and size but suffers from difficulties in providing various shapes and sizes of a display. Display panels of the matrix type, on the other hand, have relatively wide freedom in displaying different shapes and sizes of patterns.
In the case where the above mentioned matrix type of liquid crystal display is enabled by utilizing a conventional line sequential drive method, with an increase in the number of line electrodes (or column electrodes in a column sequential drive method), the period of time where a voltage is applied per line (or column), in other words, a duty factor, is shortened, presenting a cross-talk problem. A satisfactory contrast ratio is not available because a threshold voltage level of liquid crystal material is not definite and response thereof is dull. Several attempts to solve these problems have been suggested:
(I) the development of a liquid crystal material manifesting a swift response; PA0 (II) the development of a liquid crystal material having definite threshold properties; and PA0 (III) the design of an enabling circuit which further develops a well known 1/3 bias method into a 1/n bias method while allowing a wide range of an operating margin (.alpha.:V.sub.ON /V.sub.OFF) by a proper selection of drive voltages of column signals and line signals depending upon the number of lines.
Although research activities have been directed toward both sides of new liquid crystal materials and drive methods, a high capacity, high contrast display has not, as a matter of fact, been reduced to practical use as yet.
A liquid crystal display is very attractive for use in a digital wristwatch thanks to the low power consumption and low cost features thereof. A prior art wristwatch display is normally of the segment type. These days, there is a great requirement for a digital display wristwatch with multi-faculties for storing monthly calenders or telephone numbers or the like and, if necessary, displaying these contents. There is further a trend to display not only digits but also alphabetical characters. The segment type can not accomplish such a trend nor could the XY matrix type provide a high contrast due to the above problems.
It is therefore an object of the present invention to provide an XY matrix type liquid crystal which is free of the above described problems. According to the present invention, in the case where more than one kind of display pattern is to be displayed using substantially the same line or lines (a column or columns for a column sequential drive method), only line (or column) electrodes associated with a predetermined display are supplied with a voltage. The period of time where a voltage is applied per line or per column (that is, a duty factor) is switched in accordance with a display pattern which is about to be displayed. As an alternate, a drive voltage may be switched in accordance with the number of lines used. As a result, a duty factor is kept at the maximum to ensure the highest contrast during display operation.